Desalinization is the removal of salts and other chemicals from seawater or saline water to obtain pure, fresh, distilled water as the desired product. Methods of desalinization include evaporation, distillation, multi-effect evaporation, multistage flash evaporation, thin film distillation, reverse osmosis, freeze crystallization, ionic separation and electrodialysis.
In a distillation method of desalinization, it is desirable to assist the distillation by creating a partial vacuum because less energy is needed to boil water under low-pressure conditions. At standard atmospheric pressure at sea level, water boils at 100.degree. C. At lower pressures than standard, water boils at temperatures less than 100.degree. C. For example, water boils at less than 100.degree. C. at high altitude where the atmospheric pressure is lower than the standard pressure at sea level. Mountain climbers use less propane at altitudes of 15,000 feet to boil a given amount of water than it takes to boil that same quantity of water at sea level.
One example of a distillation method utilizing low-pressure conditions is the Friedman U.S. Pat. No. 2,975,107 issued Mar. 14, 1961. In one embodiment, Friedman discloses a distillation chamber and a combined vacuum and condensation chamber. In operation, the distillation chamber is filled with seawater and the vacuum chamber is filled with apparently fresh water. The chambers are heated and steam produced in the vacuum chamber is exhausted to the atmosphere. Subsequently, the vacuum chamber is closed relative to the atmosphere and opened relative to the main chamber, and heating of the vacuum chamber is discontinued. As the vacuum chamber cools, a vacuum is formed in the chambers. As the distillation chamber is heated to boil water in the low-pressure conditions, steam passes from the distillation chamber to the vacuum and condensation chamber where a refrigeration apparatus condenses the steam.
One problem with a distillation apparatus such as disclosed by Friedman is that it utilizes a closed chamber. The undesirable salt by-products of the desalinization process must be removed from, and more seawater added to, the closed distillation chamber before the desalinization process can begin anew.
Another problem with a distillation apparatus such as used by Friedman is that apparently fresh water must be used to start the desalinization process. In one embodiment, Friedman creates a vacuum in a vacuum chamber by boiling water, which is apparently fresh, unsalted, nonsaline water. After water has been boiled in the vacuum chamber, Friedman closes the vacuum chamber to the outside atmosphere and allows steam to condense in the same chamber to produce distilled water.